Organic materials with a high refractive index have been increasingly used in the fields of resin lens, optical devices, optical film, information storage, etc. Photocuring is a highly efficient approach to obtaining optical coating and optical adhesive layer. Highly refractive materials with photocuring functionality have exhibited a robust tendency for development, and shown increasingly significant application values in many fields, including backlight-brightness-enhancing films of LCD, LED encapsulations, protective coatings of panels of instrument and digital devices, etc. With a continuous growth of application demands, curable systems with a relatively high refractive index have been reported successively by some patent documents in the recent years. A Chinese patent application, CN1777822A, provides a single-phase, essentially solvent-free, polymerizable liquid composition comprising a polymerizable liquid and dissolved therein an organo-group 4, 5 or 6 compound, wherein the composition is polymerizable under the action of an externally applied influence. A Chinese patent for invention, granted under No. CN100355795C, provides a curable composition comprising multifunctional (meth)acrylate, substituted or unsubstituted aryl ether (meth)acrylate monomer, and polymerization initiator. The composition exhibits a high refractive index, and can be polymerized to provide a film with superior performance. US 2008/0075959A1 discloses a kind of photocuring monomers with high refractive index based on bromo-substituted fluorenyl, used for fabricating optical protective film. U.S. Pat. No. 7,491,441 reports an aromatic thio acrylate, such as diacrylate based on 4,4′-thiobisbenzenethiol or naphthalenedithiol; this curable compound has a relatively high refractive index and can be used for the durable hard coatings of display panels. U.S. Pat. No. 6,656,990 provides a curable organic-inorganic hybrid composition composed of metal oxide nanoparticles and organic components with high refractive index, and the compound can be used for making telecommunication optical waveguides.
However, the prior products mentioned above still cannot meet current demands. At present, there is still a need for curable monomers easy to prepare and cure and its cured products with controlled refractive index, so as to meet such requirements as protection and brightness enhancement for surface protective layer of LED devices, camera lens, and panels.